I am absolutely unable to reproduce your results locally; I suggest we arrange a TeamViewer connection to take a look at your system and determine what's going on. Neither on clean virtual machines nor on any physical machine that I or my other customers have access to has this issue been witnessed before.

I'm also curious whether your reads match the already compressed data size.example: 40 gb of files compressed into 25 gb, does it show 25 gb of reads?Or you can watch the reads MB/s. If already compressed drive, it should say mostly 0 right?

In my case it does, why would it have to read files that are already LZX compressed if it can skip these?

Yes, data should not be read if its compression state already matches the target compression state, which you are stating to be LZX to LZX on your system.

Anything could be the cause. I would be suspicious of backup, disk imaging, or anti-virus software that may have installed their own drivers, and as such may be interfering with Windows 10's normal operation. If they are trapping and rerouting API calls, and they don't understand the new Windows 10 compression 100%, these kinds of issues could occur.

Do you have any such products installed? If so, your only recourse would be to contact the manufacturers and request fixes at their end.

DriveSpace 6 would not itself be able to work around this issue, since its already doing everything "by the book".